158.9400 Interference

[BlueDevil]

Trying to find the station/transmitter causing interference on 158.9400MHz possibly operating out of North Central Idaho or the Idaho Panhandle. The station is transmitting with a CTCSS Tone of 179.9Hz. No voice is ever heard and no CW ID or other station identification is heard. All I can hear is dead carrier with what sounds like a MDC1200 signaling system. The signal seems to be most active during the hours of 0800-1300.

Here are some YouTube video clips of my observations of the interference.
https://youtu.be/_2oEKwyRPDw
https://youtu.be/L4VS5fhpicw

 

[BlueDevil]

Trying to find the station/transmitter causing interference on 158.9400MHz possibly operating out of Eastern Washington or Northern Idaho. The station is transmitting with a CTCSS Tone of 179.9Hz. No voice is ever heard and no CW ID or other station identification is heard. All I can hear is dead carrier with what sounds like a MDC1200 signaling system. The signal seems to be most active during the hours of 0800-1300.

Here are some YouTube video clips of my observations of the interference.
https://youtu.be/_2oEKwyRPDw
https://youtu.be/L4VS5fhpicw

 

[bravo14]

Trying to find the station/transmitter causing interference on 158.9400MHz possibly operating out of Eastern Washington or Northern Idaho. The station is transmitting with a CTCSS Tone of 179.9Hz. No voice is ever heard and no CW ID or other station identification is heard. All I can hear is dead carrier with what sounds like a MDC1200 signaling system. The signal seems to be most active during the hours of 0800-1300.

Here are some YouTube video clips of my observations of the interference.
https://youtu.be/_2oEKwyRPDw
https://youtu.be/L4VS5fhpicw

I've heard this before when I lived in a different area. Could it be possible someone is keying the radio and or a trunk system giving out false ctcss?

 

[NDRADIONUT]

Did u check the db for that area ??

 

[BlueDevil]

I did check both the RadioReference and the FCC database for stations holding a license for the same frequency. I am working on contacting those licensees to see it could possibly be something with their system. Our repeater is located in Southeastern WA at just over 5600ft so the geographical area that we could be getting interference from covers a 3 state area (WA, OR, ID) and probably easily 200+ mile radius. This interference is relatively new, we have only noticed it over the last 3-4 weeks and have never had any issues in the past. All the licensees that I could find who share this same frequency have had a license for this frequency for several years. So now I have to start to consider folks who maybe operating outside of their license or without a license as well.

 

[NDRADIONUT]

Is it on the same pl tone that you use ? You could also use a beam to get a direction on it....

 

[Volfirefighter]

That frequency is part of a group of VHF frequencies used by the RCMP in Canada. Could it be carrying that far?

 

[BlueDevil]

I guess I wouldn't completely rule it out. It is interesting to me that we have just now started to experience problems when we have been operating our repeater without any issues or interference for many years. We haven't changed any of our hardware or operating location.

 

[BlueDevil]

Here is a video of what the interference sounds like when we are trying to use our repeater system while the other station is transmitting on our same repeater input frequency.

https://youtu.be/7pAD7KzXbLY

 

[Vizwar]

Trying to find the station/transmitter causing interference on 158.9400MHz possibly operating out of Eastern Washington or Northern Idaho. The station is transmitting with a CTCSS Tone of 179.9Hz. No voice is ever heard and no CW ID or other station identification is heard. All I can hear is dead carrier with what sounds like a MDC1200 signaling system. The signal seems to be most active during the hours of 0800-1300.

Here are some YouTube video clips of my observations of the interference.
https://youtu.be/_2oEKwyRPDw
https://youtu.be/L4VS5fhpicw

Sounds like Kenwood FleetSync, or maybe EDACS analog signalling, which is what WS DOT uses.

Are there other systems at your repeater site? Sometimes the source can be a lot closer than you think. Especially when a new site tenant moves in without the proper filtering, or if your own repeater lacks the filtering needed for a shared site.

 

[BlueDevil]

This is the only radio at the site. There is a Verizon tower near by but the interference decreases as I get closer to the tower. I would think that the interference would be much more consistent and continuous if the Verizon tower was interfering.


Cheers,

Brandon

 

[Vizwar]

Ah ok. Here's some other things to maybe consider... Disclaimer: Totally off the cuff, spit-balling it here...

Is it opening your repeater squelch and being repeated or is it opening your end-user squelch? Depending which of these is occurring (sounds like it's hitting your repeater from what you said earlier and the videos) it's a clue as to how far away it might be.

If your repeater receive filtering is only a 4 can duplexer and nothing else, or worse, it's on a Motorola R1225 repeater, it might be a (new?) adjacent channel over driving the repeater's receiver. Or someone else's power amp is drifting or spurring onto yours. The point being, you may have to consider transmitters not on your frequency as potential offenders.

You might enlist the assistance of folks around the region to see if they can hear it and how strong, to narrow down where it might be coming from. You'll need to provide your uplink frequency as well since VHF doesn't have a specified offset. I'm in Western WA so it's unlikely I'll hear it, but next time I'm at a high site I'll give a listen.

Consider talking to local radio shops to see if they've recently put someone one the air or changed out someone's repeater. Again, provide both your uplink and downlink frequencies.

You can file a complaint with the FCC, and you probably should if this persists, but don't get your hopes up.

 

[BlueDevil]

Vizwar thanks for the comments, thoughts, and time.

Our repeater is a Motorola XPR8300 with a 4 Cavity Telewave Duplexer. It has been operating well for several years now. Both our repeater input (158.9400) and output (155.1750) frequencies are CTCSS protected using a tone of 136.6Hz. The interference is occurring on our repeater input (158.9400) frequency and is being transmitted with a CTCSS tone of 179.9Hz. The interfering signal is not opening our repeaters receiver. The interference comes in when someone within our agency is trying to use the repeater with a similarly weak signal. When someone on our system successfully opens the repeater using the right PL tone the receiver is now open and has competing signals of similar strength. The result being severe distortion and unreadable transmission. Strong signals into the repeater are able to over power and drain out the interfering signal as if there wasn't any competing signals.

The interfering signal seems to be the strongest on the 158.9400 frequency which is the exact input frequency to our repeater. When using my Yaesu VX-150 at the site the other day I moved off frequency and even just 5Mhz up or down resulted in a weaker signal. With that said I have searched the FCC database for frequencies relatively close to our repeater input frequency just in case there was a close station transmitting slightly off our frequency. I didn't find anything that really caught my attention.

I have been sending some emails out to people and organization in the region asking for any help that they might be able to offer. I have already received replies from a few. I have spoken with the FCC and was advised that I should try to conduct my own investigation to the most of my ability due to their decreased funding and staffing levels.

 

[NDRADIONUT]

I bet the fcc wont pay you either... Lol

 

[BlueDevil]

I am in fact paying them!

 

[kd7kdc]

There is a regional interference committee that meets in Spokane Valley monthly. You might try to get ahold of them for assistance. I will listen and see if I can hear it the coming week from my home in north Spokane. I seem to remember some transmissions in the past have sounded like SCADA through a repeater.

 

[ecps92]

VHF has had some openings of late in your area, so YES, it could carry that far
VHF Propagation Map

That frequency is part of a group of VHF frequencies used by the RCMP in Canada. Could it be carrying that far?

 

[kayn1n32008]

That frequency is part of a group of VHF frequencies used by the RCMP in Canada. Could it be carrying that far?

No it is not. Please do some research before posting crap. While the RCMP may have it in thier radios in BC, it is likely only used to communicate with truckers. They have a bunch of simplex channels for thier exclusive use below 144MHz. 158.940 is part of what we call the 'Basic 10'. Primarly used as a VHF equivilant of CB. Majority of users are truckers. Although it can be used as a resource road frequency it is mostly used as a BS-ing channel, kinda like CB ch 6. Ch 19 equivilant would be LAD 1. It is called LAD 2 in western Canada, LAD is short for Logging ADministration.

 

[kayn1n32008]

There is a regional interference committee that meets in Spokane Valley monthly. You might try to get ahold of them for assistance. I will listen and see if I can hear it the coming week from my home in north Spokane. I seem to remember some transmissions in the past have sounded like SCADA through a repeater.

It may even be a taxi MDT system. I really do not think it would be coming from Canada. After watching your video, i know a service like SCADA or a taxi MDT would never likely be licensed for operation on 158.9400 in BC or Alberta.

 

[NDRADIONUT]

There are no pl tones or data on those lad freqs. In canada...
Also, ideas are not crap...